Automatic circuit breaker system



Patented Aug. 11, 1936 AUTOMATIC CIRCUIT BREAKER .SYSTEM Alan S.FitzGer-ald, Wynnewood, Pa., assignor to General Electric Company, acorporation of New York Application March 10, 1933, Serial No. 660,268

13 Claims.

My invention relates to automatic circuitbreaker systems suitable forapplication to director alternating-current circuits and moreparticularly to such systems in which all mechanical relays, switches,and moving parts are eliminated, and the desired control is efiected byelectricvalve circuits.

The present application is a continuation-inpart of my copendingapplication, Serial No. 530,887, filed April 1'7, 1931, and assigned tothe same assignee as the present application.

Heretofore, there have been devised numerous arrangements includingelectromagnetic and mechanical relays, switches and other moving partsfor effecting the operation of a circuit breaker interconnecting asupply circuit and a director alternating-current load circuit. Many ofthese arrangements of the prior art are extremely complicated andinvolve the use of moving parts and contacts, which are subject to wearand deterioration in use, and very sensitive mechanical and electricaldevices, which require frequent calibration, all of which result inrelatively high maintenance costs.

It is an object of my present invention to provide an improved automaticcircuit-breaker system including electric valves which will overcome thedisadvantages of the arrangements of the prior art and which will besimple and reliable in operation.

It is another object of my invention to provide an improved automaticcircuit-breaker system including electric valves in which all movingparts and contacts are completely eliminated.

It is a further object of my invention to provide an improved automaticcircuit-breaker system including electric valves by means of which adirector alternating-current load circuit may be disconnected from itssupply circuit after a predetermined time interval and reconnectedthereto after another predetermined time interval.

In accordance with one embodiment of my invention, a load circuit isconnected to a supply circuit through a circuit-interrupting means,preferably comprising a pair of electric valves each provided with acontrol grid. The grid potentials of the electric valves, which normallyhave a phase relation with respect to the anode potentials of the valvessuch that the valves are fully conductive, are shifted to substantiallyphase opposition with respect to their anode potentials in response topredetermined abnormal load conditions. This shift in phase of the gridpotentials is accomplished by means of a pair of auxiliary electricvalves operating upon a phase-shifting circuit controlling the grids ofthe main electric valves. In order to impart a definite time delay tothe operation of the circuit-interrupting means, the grids of theauxiliary electric valves are excited with a potential across acapacitor which is charged at a fixed predetermined rate upon theoccurrence of predetermined abnormal conditions on the load circuit,this rate being independent of the magnitude of the abnormal conditions.The circuit-interrupting means may be reclosed after a predeterminedtime interval by discharging the capacitor at a predetermined rate, asthrough a resistor,

For a better understanding of my invention, together with other andfurther objects thereof, reference is had to the following descriptiontaken in connection with the accompanying drawing, and its scope will bepointed out in the appended claims. The single figure of the drawingillustrates .my invention as applied to an automatic circuit-breakersystem for controlling the interconnection of a direct-current loadcircuit and an alternating-current supply circuit.

Referring now to the drawing, I have illustrated an arrangement forcontrolling the connection and disconnection of a load circuit Ill and asource of alternating current ll. The load circuit i0 is illustrated asa direct-current circuit energized from the circuit 1 I through afull-wave rectifier comprising a transformer l2 and electric valves i3and l4,-although it will be apparent that electric valves l3 and I4 maybe reversely connected in parallel in a well-known manner in case it isdesired to energize the load circuit ill with alternating current. Itwill also be understood that the supply and load circuits may beinterconnected by means of any suitable circuit-interrupting apparatus,in which case the operation of such means will be controlled by theelectric valves l3 and 54. Electric valves 83 and M are each providedwith an anode, a cathode, and a control grid, and may be of any of theseveral types well known in the art, although I prefer to use valves ofthe vapor-electric discharge type in which the magnitude of the currenttransmitted by the valves is independent of the magnitude of the gridpotential, assuming only that the grid potential is more positive thanthe critical value which is necessary for maintaining the valvesnon-conductive. This type of valve is sometimes referred to in the artas a grid glow tube. The conductivity of valves of this type may bereadily controlled by impressing alternating potentials upon the gridsand anodes of the valves and varying the phase Aug. 11, 1936. A. s. FlTZGERALD 2,050,882

AUTOMATIC CIRCUIT BREAKER SYSTEM Filed March 10, 1953 Inventor: Alan S.FitzGeralcl,

ps MEJWZZW Hi 5 Atbovne l that the load circuit is thereafterreconnected to the supply circuit after another predetermined intervalof time.

While I have described what I at present consider the preferredembodiment of my invention, it will be obvious to those skilled in theart that various changes and modifications may be made without departingfrom my invention, and 1 therefore aim in the appended claims to coverall such changes and modifications as fall within the true spirit andscope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

1. In a protective system, an electric circuit, a

circuit interrupter therefor, energy storage means,

means responsive to a predetermined abnormal.

condition on said circuit for varying the energy stored in said storagemeans at a rate independent of the magnitude of said abnormal condition,and means responsive to a predetermined storage of energy in saidstorage means for operating said interrupter.

2. In a protective system, a supply circuit, a load circuit, meansincluding an electric valve interconnecting said ciruits, energy storagemeans, means responsive to a predetermined abnormal condition of one ofsaid circuits for varying the energy stored in said storage means at arate independent of the magnitude of'said abnormal condition, and meansresponsive to a predetermined storage of energy in said storage meansfor rendering said valve non-conductive to disconnect said circuits.

3. In a protective system, a supply circuit, a load circuit, meansinterconnecting said circuits including an electric valve provided witha control grid, phase-shifting means for exciting said grid from one ofsaid circuits normally to render said valve conductive, a condenser,means responsive to a predetermined overload on said load circuit forcharging said condenser at a rate independent of the magnitude of saidoverload, a second electric valve, means for varying the conductivity ofsaid second valve in accordance with the charge on said condenser, saidphaseshifting means being controlled by said second electric valve torender said first valve non-conductive to disconnect said circuits uponthe persistence of said overload for a predetermined length of time.

4. In a protective system, an electric circuit, a circuit interruptertherefor, a condenser, means responsive to an overload on said circuitfor va ying the charge upon said condenser during said overload at arate independent of the magnitude of said overload, and means responsiveto a predetermined charge upon said condenser for operating saidinterrupter when said overload continues for a definite. time interval.

5. In a protective system, an electric circuit, a circuit interruptertherefor, an electric discharge device, means responsive to an overloadon said circuit for causing said device to pass a current of a magnitudeindependent of the magnitude of said overload, and means controlled bysaid current for operating said interrupter when said overload continuesfor a definite time interval.

6. In a protective system, an electric circuit, a circuit interruptertherefor, an electric discharge device, means responsive to an overloadon said circuit for causing said device to pass a current of a magnitudeindependent of the magnitude of means responsive to a predeterminedcondition of energization of said second device for operating saidinterrupter when said overload continues for a definite time interval,

7. In a protective system, an electric circuit, a circuit interruptertherefor, an electric discharge device, energy storage means, meansresponsive to an overload on said circuit for causing said device tovary the condition of energization of said storage means at a rateindependent of the magnitude of said overload, and means responsive to apredetermined condition of energization of said storage means foroperating said interrupter when said overload continues for a definitetime interval.

8. In a protective system, an electric circuit, a circuit interruptertherefor, an electric discharge device, means responsive to an overloadon said circuit for causing said device to pass a current of a magnitudeindependent of the magnitude of said overload, a condenser, means forvarying the chargeupon said condenser at a rate determined by saidcurrent, and means including a second electric discharge device,responsive to the charge upon said condenser for operating saidinterrupter when said overload continues for a definite time interval.

9. In a protective system, an electric circuit, a circuit interruptertherefor, a grid glow tube, means responsive to an overload on saidcircuit for controlling said tube to pass a current of a magnitudeindependent of the magnitude of said overload, a condenser, means,including a resistor, for varying the charge upon said condenser at arate determined by said current, and means including an electricdischarge device, responsive to the charge upon said condenser, foroperating said interrupter when said overload continues for adefinite'time interval.

10. In a protective system, an electric circuit, a circuit interruptertherefor, a grid glow tube, a resistor, an alternating-current sourceconnected in series relationship to said tube and said resistor, meansincluding the grid of said tube for causing said tube to becomeconducting upon the occurrence of an overload on said circuit, acondenser connected in parallel relationship to said resistor, and meansresponsive to a predetermined charge upon said condenser for operatingsaid interrupter when said overload continues for a definite timeinterval.

11. In a protective system, an electric circuit, a circuit interruptertherefor, an electric discharge device having a control element, saiddevice being of a type in which an electric discharge may be started inresponse to a predetermined electrical condition of the control elementand in which the magnitude of the discharge is independent of theelectrical condition of the control element,.means including saidcontrol element for initiating a discharge in said device upon theoccurrence of an overload on said circuit and for interrupting saiddischarge upon the cessation of said overload, and means responsive tocumulative action of said discharge for operating said interrupter ifsaid overload continues for a definite time interval.

12. In a protective system, an electric circuit, a circuit interruptertherefor, an electric discharge tube containing an ionizable medium andhaving a control element, said tube being of a type in which ionizationof said medium is started in response to a predetermined electricalcondition of the control element and is maintained by a dischargecurrent in the tube, an alternatingcurrent source for energizing saidtube, means including said control element for initiating a pulsatingdischarge in said tube upontlie occurrence of an overload on saidcircuit, and means responsive to cumulative action of said discharge foroperating said interrupter if said overload continues for a definitetime interval.

13. In a protective system, an electric circuit, circuit-interruptingmeans operable to electrically complete and interrupt said circuit, anelectric discharge device containing an ionizable medium and having acontrol element, said device

